W. K. Clifford: (1845-1879) was not only a genius mathematician but also a physicist and a philosopher.
(A) The Mathematician: He was the founder of n-ways algebras (now called geometrical algebras or simply Clifford algebras). He defined these algebras as tensor product of quaternionic algebras and their extensions. He followed and improved the work initiated by Hamilton and Grassmann. He studied geometrical representations of analytic functions, non-Euclidean geometries, the theory of elliptic spaces, algebraic forms and projective geometry. His mathematical papers have been published by Macmillan and are actually republished by University of Michigan Library.
(B) The Physicist: In his paper On Space-Theory of Matter, Clifford proposed to relate matter to propagating space curvature - the idea that has found its final shape in Eintsein's theory of gravitation.
(C) The Philosopher: As a philosopher he introduced two important concepts: mind stuff and tribal self. All his philosophical papers are subordinate to his mathematical thoughts.